The present invention is directed to recovery of fresh or potable water from aqueous saline solutions from brine such as sea water and brackish water where heated pellets are used to transfer heat to the aqueous saline solution followed by flash vaporization and condensation of water on relatively cool pellets.
With drastic changes in the world energy situation and associated increases in the cost of materials, desalination processes must take a new direction. In areas where energy is no longer cheap, it appears the processes must utilize the lowest amount of and lowest cost of energy. For areas where energy is still plentiful and cheap, the emphasis for future desalination must be on reduced capital cost.
The present invention is directed to a more efficient use of energy and reduced capital cost in the field of desalination by the use of pellets.
Distillation remains the best method developed yet for large scale desalination. The manner by which heat is transferred is the heart of any desalination process. Desalination methods are described in various patents and articles. Reference is made to U.S. Pat. Nos. 3,390,078, 3,242,975, 3,640,850, 3,843,462, "Energy and the Future of Desalination: The Role of Calex," Tenth Intersociety Energy Conversion Engineering Conference, Phillips et al (1975), and "Principles of Desalination," Woodward et al, Academic Press, Chapter 4, page 117 (1966), all incorporated herein by reference.
Of the above, U.S. Pat. No. 3,843,462 issued to one of us is the most relevant and describes a process where the aqueous saline solution, to undergo desalination, is passed countercurrent to the flow of hot balls. The heated aqueous saline solution is flash vaporized and the vapors evolved condensed on moving hot balls with intermediate heating of hot balls for use in the heating cycle of the process.
A need was found to exist to improve such a process to reduce capital cost, improve thermodynamic efficiency, eliminate the energy required to move large volumes of heat transfer pellets through the system and avoid mechanical problems.